1. Field of the Invention
The present invention relates to a plasma display panel (hereinafter also referred to as a plasma panel or a PDP), and in particular to a structure of a plasma panel capable of improving a light-room contrast and realizing high luminous efficacy and high-quality display images, a method of manufacturing the plasma panel, a method of driving the plasma panel, and a plasma display apparatus including a driving device in addition to the plasma panel.
2. Description of Prior Art
Recently, plasma display devices have been expected as promising large-size thin color display devices. More specifically, since an ac surface-discharge type PDP generates discharges between electrodes disposed on the same substrate for producing a display and is driven by ac voltages, the ac surface-discharge type PDP is the most common among PDPs put to practical use because of its simple structure and high reliability. The following will explain an example of a conventional ac surface-discharge type PDP.
FIG. 1 is an exploded perspective view illustrating part of a structure of a plasma panel. Formed on an underside of a front glass substrate (a substrate facing a viewing space explained lately) 1 are transparent common electrodes (hereinafter referred to as X electrodes) 22-1, 22-2 and transparent independent electrodes (hereinafter referred to as Y electrodes or scan electrodes) 23-1, 23-2. X bus electrodes 24-1, 24-2 and Y bus electrodes 25-1, 25-2 are overlaid on the X electrodes 22-1, 22-2 and the Y electrode 23-1, 23-2, respectively. Further, the X electrodes 22-1, 22-2, the Y electrodes 23-1, 23-2, the X bus electrodes 24-1, 24-2, and the Y bus electrodes 25-1, 25-2 are covered with an dielectric 2, and then they are covered with a protective film (also called a protective layer) 3 such as magnesium oxide (MgO). The X electrodes 22-1, 22-2 and the Y electrodes 23-1, 23-2, the X bus electrodes 24-1, 24-2, and the Y bus electrodes 25-1, 25-2 are collectively named a display discharge electrode or a display electrode (or a display discharge electrode pair or a display electrode pair, to indicate that they form a pair of X and Y).
In the above, the X electrodes 22-1, 22-2 and the Y electrodes 23-1, 23-2 have been explained as transparent electrodes, this is because a brighter (high-brightness) panel can be obtained, and it is needless to say that they do not always need to be transparent. Magnesium oxide (MgO) is explained as a concrete material for the protective film 3, but material for the protective film 27 is not limited to magnesium oxide. The objects of the protective film 3 are to protect the display discharge electrodes and the dielectric 2 from bombarding ions and to promote initiation and sustenance of discharge with secondary electron emission caused by incident ions. Other materials can be used which are capable of achieving the above objects. The front glass substrate 1 combined in this way with the electrodes, the dielectric and the protective films in an integral structure is called a front plate.
On the other hand, formed on an upside of a rear glass substrate 10 are electrodes (hereinafter referred to as A electrodes or address electrodes) 11 such that they intersect the X electrodes 22-1, 22-2 and the Y electrodes 23-1, 23-2 at right angles with grade separation. The A electrodes 11 are covered with a dielectric 9, and barrier ribs 7 are formed on the dielectric 9 such that they extend in parallel with the A electrodes 11. Further, phosphors 8 are coated on inner surfaces of cavities formed by wall surface of the barrier ribs 7 and the upper surfaces of the dielectric 9. The rear glass substrate 10 combined in this way with the A electrodes and the dielectric 9 in an integral structure is called a rear plate.
A plasma panel is fabricated by bonding together the front and rear plates provided with the necessary constituent elements as described above, filling a gas (a discharge gas) for creating plasma into a space between the front and rear plates, and then sealing the panel. It is needless to say that it is necessary to bond together and seal the front and rear plates to ensure the hermeticity of the sealed package containing the discharge gas.
FIG. 2 is a cross-sectional view of the PDP of FIG. 1 viewed in the direction of the arrow b of FIG. 1, and schematically illustrates three cells which form the smallest unit of pixels. In FIG. 2, borders of the one cell are roughly indicated by broken lines. Hereinafter, cells are also called discharge cells.
In FIG. 2, the A electrode 11 is disposed halfway between the two barrier ribs 7, and the gas (discharge gas) for creating the plasma is contained within a discharge space 12 surrounded by the front glass substrate 1, the rear glass substrate 10 and the barrier ribs 7.
Here, the discharge space means a space where a display discharge for producing a display, an address discharge, or a preliminary discharge (also called a reset discharge) is generated in operation of the plasma panel as described later. More specifically, the discharge space is a space which is filled with the discharge gas, has applied thereacross an electric field necessary for the discharge, and has a spatial expanse required for generation of the discharge. Further, a display discharge space means a space where a display discharge occurs, more specifically, a space which is filled with the discharge gas, has applied thereacross an electric field necessary for a display discharge, and has a spatial expanse required for generation of the display discharge. The discharge space and the display discharge space sometimes mean a space included in each of the discharge cells, and sometimes mean a collection of the spaces included in the discharge cells.
In a color PDP, usually three kinds of phosphors for red, green and blue are coated within the cells, respectively. A trio of cells coated with the three different kinds of phosphors serves as one pixel. A space having a plurality of such cells or pixels arranged continuously and periodically is called a display space. A set is called a plasma display panel or plasma panel which includes the display space and is provided with other necessary structures such as vacuum sealing and electrode leads for external connection. Hereinafter, the plasma panel is also referred to as the PDP.
In the plasma panel, a structure integrally fabricated to seal the discharge gas therein hermetically is referred to as the basic plasma panel. In the basic plasma display panel, a surface from which visible light for display is irradiated is called a display surface, and a space into which the visible light for display is irradiated is called a viewing space.
As described above, in the basic plasma panel, there is a space containing at least the plural discharge cells arranged continuously, which is hereinafter referred to as a display space.
In this specification, the above-defined area S1 is represented by dimensions LS1a and LS1b in the directions of the arrows a and b, respectively, and the above-defined area S2 is represented by dimensions LS2a and LS2b in the directions of the arrows a and b, respectively. The areas S1 and S2 are indicated by broken lines in relevent ones of the drawings.
Let S1 be an area of a projection of a space occupied by one of the plural discharge cells onto the front substrate 1. Let S2 be an area of a window portion of the front substrate 1 through which the visible light is irradiated from the one of the discharge cells into the outside of the front substrate 1. Let S2/S1 be an area ratio of the display discharge region, an aperture ratio. An area other than the area S2, that is, the area (S1−S2) shall be called a non-aperture area, and its area ratio (S1−S2)/S1 shall be called anon-aperture ratio.
In the conventional plasma panel shown in FIG. 1, the length directions (a direction b) of the barrier ribs 7 are oriented approximately in one direction, and this structure of the plasma panel is called the straight-barrier-rib structure. In another conventional plasma panel, the length directions of the barrier ribs are oriented in at least two directions, and this structure of the plasma panel is called the box-barrier-rib structure.
FIG. 3 is a cross-sectional view of the PDP of FIG. 1 viewed in the direction of the arrow a of FIG. 1, and schematically illustrates two cells. In FIG. 3, borders between the cells are roughly indicated by broken lines. Reference character Wgxy denotes a spacing between the display electrode pair (the X and Y electrodes), and the spacing Wgxy is called a display electrode gap. In FIG. 3, reference numeral 4 denote electrons, 5 is a positive ion, 18 is a positive wall charge, and 6 are negative wall charges.
By way of example, FIG. 3 schematically illustrates that, by applying a negative voltage to the Y electrode 23-1 and a voltage positive with respect to the Y electrode 23-1 to the A electrode 11 and the X electrode 22-1, initially a discharge is generated, and then the discharge has ceased. This has caused formation of a wall charge for assisting in initiation of a discharge between the Y electrode 23-1 and the X electrode 22-1, and this formation of the wall discharge is called “address.” In this state, when an appropriate voltage of the polarity opposite from the previous one is applied between the Y electrode 23-1 and the X electrode 22-1, a discharge is generated in the discharge space between the two electrodes through the dielectric 2 (and the protective film 3). After the cessation of the discharge, if the polarity of the voltage applied between the Y electrode 23-1 and the X electrode 22-1 is reversed, a new discharge is generated again. By repeating this process, discharges are generated continuously, and these discharges are called display discharges (or sustain discharges). Such a conventional ac surface-discharge type PDP is disclosed in U.S. Pat. No. 6,333,599.